Return the root node of a binary search tree that matches the given preorder traversal.
(Recall that a binary search tree is a binary tree where for every node, any descendant of node.left has a value < node.val, and any descendant of node.right has a value > node.val. Also recall that a preorder traversal displays the value of the node first, then traverses node.left, then traverses node.right.)
Example 1:
Input: [8,5,1,7,10,12] Output: [8,5,10,1,7,null,12]
Note:
<li><code>1 <= preorder.length <= 100</code></li>
<li>The values of <code>preorder</code> are distinct.</li>